(Dev4.4) Allow @export_enum for typed dictionaries

[secretmeister2]

I think it would be very useful if you could use the @export_enum export type for typed dictionaries. Maybe have a special character in the hint string designate when you switch from key to value, or something? Or at least make it possible to have the key be displayed as a string in the inspector.

For usecase, I want to map rarities to a point value, based on a string name of the rarity. So I want to limit the key selection to "common" "uncommon" etc, and have it actually store as a string, not an int.

If there is a different way to acheive what I want to acheive, then that would be useful.

(Currently using 4.4dev4)